The present invention relates to a new and improved method of compensating for the wear of an adjustable or advanceable dressing tool for grinding wheels, by means of which a working or active surface of the grinding wheel, which is positioned in a defined plane, is dressed by an adjustable dressing amount.
In a known method of, and apparatus for, dressing a grinding wheel as disclosed, for example, in U.S. Pat. No. 4,213,277, granted July 22, 1980, an axially adjustable dished grinding wheel of a gear wheel grinding machine acts upon a workpiece by means of a working surface or face which is dressed in intervals. During the dressing operation the position of the working or active surface of the grinding wheel is controlled and the grinding wheel is re-adjusted such that the working surface thereof remains in the same position independent of the degree of wear. The dressing tool is also axially adjustable and the working surface of the grinding wheel is dressed once during a preselected dressing interval. The dressing tool is always axially adjusted in case that a preselected total amount of grinding wheel re-adjustment is not reached within the dressing interval. The dressing operation has the purpose of obtaining and maintaining a high cutting efficiency of the highly-loaded grinding wheels during the grinding of gears. The working surface or face of the grinding wheel always has to be dressed sufficiently in order to remain sharp. For controlling the position of the working surface or face of the grinding wheel in intervals a sensor is intermittently pivoted to engage such working surface or face. A contact is operatively associated with the sensor and when the contact is closed due to a certain amount of wear of the working surface then the grinding wheel is axially re-adjusted. The dressing interval has a length or time frame which depends upon the nature of the grinding wheel and which may be selected according to the amount of material which has to be removed from the gear wheel. If a certain number of re-adjustments of the grinding wheel are not reached within a dressing interval, this means that the working surface or face is not sufficiently sharp and will have to be dressed anew. Depending upon the extent by which the number of grinding wheel re-adjustments is less than the preselected number of re-adjustments, then the dressing tool is adjusted or advanced to a greater or lesser extent for the dressing of the working surface or face. Thereafter the grinding operation is resumed for the duration of the next following dressing interval and the operation as described hereinbefore is repeated during this dressing interval.
When using the known method it can thus first only be determined after expiration of the dressing interval whether the grinding wheel is sharp and works correctly. This can be disadvantageous for heavily used grinding wheels because the grinding operation is then accomplished for a certain amount of time with an insufficiently sharp working or active surface or face. The shortfall in the number of grinding wheel re-adjustments during the preceding dressing interval only permits an indirect conclusion with respect to the degree of wear of the dressing tool, because it is simply assumed that the dressinng tool was insufficiently effective. during the preceding dressing operation due to wear thereof, so that it has to be correspondingly adjusted during the following dressing operations. The success of the dressing operation after re-adjustment again only can be detected after expiration of the subsequent dressing interval. In the prior art method the degree or extent of wear of the dressing tool cannot be measured and the adjustment thereof only can be accomplished in steps, so that improvements are required as concerns the compensation for the wear of the dressing tool.